Radio circuit selector switch



Nov. 30 1948. G. R. PENNINGTON 2,455,137

RADIO CIRCUIT SELECTOR SWITCH Original Filed May 25, 1942 INVENTOR GORDON R. PENNIIGIUN Patented Nov. 32, 1948 RADIO CIRCUIT SELECTOR SWETCH Gordon It. Pennington, Bloomfield Hills, Mich.

Original application May 25, 1942, Serial No. 444,331, now Patent No. 2,422,253, dated June 17, 1947. Divided and this application April 24,

1947, Serial No.

This invention relates to an electrical circuit selector switch, and especially to a selector switch for use in connection with automatic program selectors for radio receiving sets.

The present application is a division of my co-pending application, Serial No. 444,331, filed May 25, 1942, now Patent No. 2,422,253, issued June 17, 1947.

The object of my invention is to provide an electrical selector switch which is of simple construction, adapted to low cost, quantity production and which is highly eiiicient for the use intended.

A further object is to provide a compact electrical selector switch adapted to select a plurality oi selector circuits one at a time.

Another object is to provide a selector switch in which the rotatable contact plug thereof is so constructed as to accommodate substantially wide manufacturing tolerances in the bore of the switch panel and of the plug and yet obtain a good pressure contact and fit when the plug is assembled in the panel.

A more specific object is to provide a selector switch in which the contact plug thereof comprises a stem having a hollow thin walled construction including a projecting contact making bead, the portions of which are disposed in a generally spiral arrangement about said stem, the stem being distortable at each section under the bead so that the plug may be assembled for rotation in a switch panel bore smaller than the free diameter of the plug whereby to facilitate proper fitting of the plug in the panel and the obtaining of oodelectrical contact at each rotative position of the plug where a circuit connection is to be made.

Another object is to provide a selector switch in which the bore of the switch panel is of slightly smaller size than the normal free size of the plug therein, the said plug comprising a hollow resilient structure adapted to accommodate itself to the switch bore by distortion from its normal shape lengthwise of the plug so as to exert a radial pressure against the wall of the bore for obtaining good electrical contact, yet be readily rotatable to different positions.

A still further object is to provide a selector switch including a contact panel and a selector plug in which the plug obtains at least a three point contact with the bore of the contact panel in any plane through the axis of the plug.

Other objects and novel features of my invention will be apparent from the following description and from the drawing which illustrates my 14 Claims. (Cl. 200-8) invention as applied to an eight position switch for an automatic program selector described and shown in my said co-pending application.

In the drawing in which similar numerals designate similar parts of the construction,

Figure l is a cross-sectional view of a switch* embodying my invention, portions of the switch panel being broken away.

Figure 2 is a cross-sectional view taken on the line 22 of Figure 1.

Figure 3 is a cross-sectional of the switch rotor or plug.

Figure 4 is a developed view of the cylindrical surface shown in Figure 1 illustrating the contact area of the plug in the position shown in Figure 1 superimposed on the contact areas on the surface of the bore in the switch panel.

Figure 5 is a sectional view of the selector head taken at 5-5 of Figure 1.

Referring to Figures 1 to 5, the numeral l0 generally designates a switch contact body, block, or panel having a cylindrical bore or hole ii in which is positioned the electrical conducting or contact plug, or rotor generally designated by numeral l4 and adapted for relative rotation with respect to the switch-panel Ill. The panel Ill, in the form illustrated, preferably comprises a laminated structure built up of a plurality of thin metallic sheets (one for each of the broadcasting stations from among whose programs selection view of a portion is to be offered) IE to 22 inclusive of electrical conducting metal such as hard copper or brass alternating with and cemented between sheets 23 to 30 inclusive, of plastic or other (relatively) electrically noncc-nducting material.

Each of the metallic sheets is pierced prior to assembly by a hole 3| which is circular in shape except for a radially inwardly projecting tab generally referred to by the numeral 32. (See Figure 2.)

As seen in Figures 2 and 4, the tabs 33, 34, 35 and 38 of conductor sheets l6, I1 and i3 and I9, respectively, in the switch illustrated, are preferably arranged in alignment axially of the plug; and the tabs 31, 38 and 39 of the conductor sheets 20, 2| and 22, respectively, are also arranged in alignment with each other axially with the plug but are, as a group, angularly offset by the angle alpha (see Figure 2) from the group of tabs 33 to 38, inclusive, this'angle alpha being substantially 45.

After assembly, the plastic sheets are drilled through the hole in the metallic sheets to provide the cylindrical hole or bore II. It is to be ob served that, when the bore I2 is drilled through access? the panel it, it is so located, and of such a diarrn eter, as to out off a portion ill) (see "Figure 2) cl eachof the tabs 33 to 39 inclusive, but does not otherwise cut through or intersect the metal sheets if} to 22 inclusive, by being of slightly less diameter than the holes in the metal sheets so as to leave an annular clearance G24 (see Figure 2) between the bore (12 and the periphery oi the hole ill in the metal sheets which may be and preferably, are filled with electrically non-con= ducting plastic during the cementing operation, except where the tabs are located, thus providing electrical contact surfaces at and only at the tab locations.

The amount of clearance 62 is pro-set to be sufficient to allow for expected variations in hole locations in production when switch panel having a plurality of plugs is provided. The tabs 32 are preferably made of sumcient length to make sure that they will be trim-med during the drilling operation of the panel to form contact areas 43 to 49 inclusive on the tabs 32 to 38 inclusive respectively of Figure 4 flush with the surface of the bore 12 as seen in Figure 2. Each of the metal sheets it to 22 will be provided with a. connection tab (not shown) projected beyond the plastic sheets to which circuit connections may be made.

The rotatable plug l4 comprises a thin walled tubular member or stem 50 of resilient character preferably of hard drawn brass and tinned on the outside, having an expanded portion M at one end which is press fitted into and/or soldered to a head piece, or knob, 52 whereby the rotor may be manually rotated. The head b2 may beprovided with a suitable pointer or indicating means, for example a fiat 54, for indicating angular position of the plug with respect to the horizontal or vertical or to some not shown, which may be on the plastic sheet 23.

The opposite end of the rotor it also has an expanded portion 55 to receive a metallic contact cap 65, preferably of brass, which is'press fitted, and preferably soldered to the tube Ml after assembly of the rotor in the panel it.

The tubular member Bil has a raised spiral ridge which is preferably raised .00?" to .010" on all except the ends of the. tube, for example, as by a radial coining operation. In the switch illustrated the helix angle or this ridge is such as to produce a quarter of a revolution (90) of the ridge around the rotor in the distance between any two adjacent conductor sheets id to 22 inclusive.

It will be understood that the flat as must, of coursev be accurately positioned angularly with respect to the spiral 68. This positioning can readily be accomplished in an automatic machine by machining the flat while the assembly of the head 52 and the tube 53 (soldered at an earlier operation) is gripped in the die which forms the ridge 58. This die is machined so as to make the top of the ridge 58 project a few thousands of an inch outside of a cylinder which would just fit easily into thedrilled hole of bore i2 and which would substantially coincide with the cylindrical surface of the expanded portions ill to 55 of the tube or stem 50.

Thus, when a rotor whose free diameter is greater than the diameter of the bore 12 is inserted in the bore, the stem or tube 50 is, in order to be fitted therein, distorted slightly from its normal shape, as in Figure 3 to that somewhat exaggeratedly shown in Figure 1, from which it will be evident that the tube distorts or bends immediately under each point of contact of the markings or other indices spiral with the wall of the bore in the panel, giving the plug stem iii] a twist eilect. This distor tion, in combination with the resiliency of the tube, which, as stated previously, is preferably of hard drawn brass, assures positive pressure between the top of the spiral ridge and the contact areas it to inclusive which as previously stated, flush with the walls of the drilled hole i2. lifter the rotor id is inserted in the bore i2 a contact cap lid is firmly pressed on the cylindrical raised portion to hold the rotor endwise in the bore iii of the panel and also to provide an electrical contact surface for contact with a circuit completing contacting finger so shown in phantom in Figure 1.

As seen in Figures 1 and i the rotor id is in a position in which the spiral ridge 58 contacts the conductor sheet it through the contact area :38 of the tab 33 so as to create an electrical circuit path between conductor sheetv l6 and the spring contact ti) through the tube 50 and cap 58, the contact 80 and the conductor sheet I, being connected with, for example, a radio broadcast circuit in the manner set forth in my copendlng application aforesaid.

If the rotor is turned 45 counterclockwise (as seen from the front of the panel), the raised ridge 58 will contact the conductor sheet 20 through the contact area 41 of the tab 31. Further rotation in the same direction will establish contacts at 45 intervals with the conductor sheets in the order ill, 2|, i6, 22 and i9, respectively, through their contact areas 44, 48, 85, 49, and M respectively. an additional rotation of 45 in the same direction (or 45 clockwise rotation from the position shown in the drawing) after making contact with the contact area it will establish no contact and is therefore the oil position of the switch.

It will be observed as stated above, that the contact areas 41, 4a and 49 are angularly offset by the angle alpha from the contact areas ll to 45 inclusive. This arrangement is preferred so that the portion 62 of the spiral ridge 58 in Figure 4 will not make contact with the contact area.

:31 at the same time as contact is made with contact area 33 and similarly as to other contact positions. It will also be noted that the sheets i8, ii, 48 and it, alone, would provide a 4 pole switch in which these separate sheets would be contacted successively by rotational steps of the rotor.

It will be seen from Figure 1 that the spiral ridge E58 is of such length as to enable selective contact of each of the conductor sheets it to 22 inclusive to be made during a complete revolution of the plug it. Preferably this length will, in the preferred embodiment be approximately one and one-hall turns, such having the advantage that any plane passed through the rotational axis of the spiral ridge will inter-sect the latter at at least three points in contact wtih the wall of the bore i'z so as to obtain a good lit and good operation in either direction of rotation, and good electrical contact at the time the spiral 58 engages one of the conductor sheets, all this being facilitated by the nature of the contact ridge and the slight distortion of the rotor tube, or stem heretofore referred to.

Although I do not desire to be precise as to the number of turns of the spiral ridge it will be manifest that when less than the one and onehalf turns is employed the advantageous three point contact will be lost in some planes and when one and one-half turns are exceeded there will be seems? more than three points of contact in some planes resulting in unnecessary thickness. and therefore cost, of the panel Ill.

While the particular selector switch structure hereon described is well adapted for carrying out the objects of the present invention it will be understood that various modifications, changes, and substitutions may be made without departing from the spirit thereof. For example, although not preferred, the spiral ridge may be in the form of an interrupted spiral. Moreover, the invention may be applied to other uses than radio program selectors. The present invention is therefore to be construed to include all such modifications, changes, substitutions and applications as may come within the scope of the following claims.

I claim:

1. A circuit selector switch comprising in combination, a rotatable plug having a thin-walled resilient metallic stem the surface of which is provided with a projecting bead extending spirally about said stem, and a panel having a generally cylindrical bore adapted to receive the stem of said plug, said bore being of slightly smaller diameter than the free diameter of said stem outside said bead whereby the section of said stern under said bead is slightly distorted to provide a spring-like pressure fit with said bore when said plug is assembled therein.

2. A circuit selector switch as claimed in claim 1, wherein the said bead projects sufficiently from the surface of aid stem to accommodate said distortion.

3. A circuit selector switch as claimed in claim 1, wherein said bead extends in a spiral of approximately one and one-half turns.

4. A circuit selector switch comprising in combination a rotatable plug having a normally straight thin-walled tubular stem resilient in character, the surface of which is provided with a projecting metallic contacting ridge extending generally spirally about the axis of said stem, and a contact panel having a generally cylindrical bore of slightly smaller diameter than the free diameter of said stem outside said ridge, said stem being adapted to resiliently assume a wavy character when assembled in said panel, to facilitate pressure contact of said ridge with said bore.

5. A circuit selector switch comprising in com bination, a rotatable contact plug having a cylindrical stem presenting a resilient metallic contact ridge extending in a spiral about the axis of said stem and projecting above the adjacent surface of said stem, and a contact panel of insulation material having in the body thereof a metallic contact, said panel'having a bore for receiving said stem and said contact presenting a contact surface of limited area substantially flush with the surface of said bore; said stern having a free diameter outside said spiral ridge slightly greater than that of said bore and said spiral ridge being resiliently contractable when said plug is assembled in said panel whereby to exert outward pressure against said metallic contact when in radial alinement therewith.

6. A circuit selector switch comprising in combination, a rotatable contact plug having a hollow thin-walled resilient metallic stem the surface of which is provided with a projecting contacting bead extending generally spirally about the axis of said stem, and a contact panel having a generally cylindrical bore of slightly smaller diameter than the free diameter of said stem outside said bead, and having a plurality of metallic contacts axially and circumferentially spaced in the said bore and substantially flush with the surface of said bore. said stem when assembled in said bore being resiliently contractable therein whereby said head exerts outward pressure against the said metallic contacts when in radial juxtaposition thereto.

7. A selector switch comprising in combination, a rotatable contact plug having a hollow thin-walled metallic stem provided with a circuit making ridge extending spirally about the axis of said stem, and a contact panel having a bore adapted to receive said stem for rotation therein, said panel comprising alternate layers of metallic sheets and insulating material, said metallic sheets each adapted to form a part of an electrical circuit and each said metallic sheet having a tab thereof exposed in said bore for making contact with said spiral ridge at a predetermined rotational position of said plug.

8. A selector switch comprising in combination, a rotatable contact plug having a resilient hollow thin-walled metallic stem provided with a circuit making ridge extending spirally about the axis of said stem, and a contact panel having a bore in which said stem is mounted for rotation, said panel comprising spaced apart metallic members adapted to form part of electrical circuits and each member having a portion thereof exposed in said bore for making contact with said ridge at predetermined rotational positions of sa d plug; the stem of said plug prior to assembly in said bore having a free diameter outside said ridge slightly in excess of said bore whereby a reduction in the stem shape occurs in assembly to facilitate pressure contact between said ridge and exposed portions of said members at said predetermined positions.

9. A selector switch comprising in combination, a contact panel comprising insulation material having a cylindrical bore therein, a plurality of metallic contacts presenting areas of limited extent fiush with the wall of said bore, a hollow rotatable plug in said bore presenting a spiral metallic ridge adapted to bear upon a limited area of the wall of said bore and adapted to make contact with said areas of said metallic contacts in accordance with predetermined rotational positioning of said plug, said spiral ridge having a free diameter greater than said bore when disassembled from said bore and said spiral ridge being of resilient character and adapted to resist reduction in the free diameter thereof such that when said plug is in assembled relation with said bore said ridge may effect a pressure contact with said metallic contacts at said predetermined positions of said plug.

10. A selector switch comprising in combination, a rotatable contact plug having a resilient, hollow, thin-walled metallic stem presentin a circuit making ridge extending in the form of a spiral about the axis of said stem, an insulated contact panel having a cylindrical bore in which said plug is rotatably mounted, said panel comprising a plurality of metallic contact members separated by insulation material, said members each having a portion thereof exposed in said bore and said portions being arranged in a plurality of groups with the said portions in each group in series and intersecting a plane passing through said axis, each group being positioned at a different rotational position of said plug such that during rotation of said plug said ridge will make contact successively with said portions of said groups in accordance with their axial position and contact wiih only a single c522 said gc-cr Zions m7 any cm gccsiilcn cf said #5 5.

11. A sciccicc mwci'i comprising in ccmcincp clam, a laminated panel having iaycr: ci" mciaiiic maiexmi and inwiaticn m2,- Lcxial, an cgccming' iii having a wall immcci by said insuici in material and presenting limited. spaccd edge cf flush with said Wflli, and conic/ct plus in swim opcning having a resilient imiicw thin-waiicci pm= viding a resilient contact in picssurc ccn iaci with said Wail anal adapted in m l-I1 ccmmct with acid edge areas @i said mcwiiic sheets at predetermined x'cmtizmal pcsiiaicm m plus.

12. A sclcc'fior switch {ES ciaimeci in claim 11, wherein the plug has an indexing m; one and and circuit ccnmct means at cine? and.

13. A rctctcbic contact plug icc selcc'tcr switch comprising a rcciiiemi. hciiow thin wciicii cylindrical stem having a narrow raised contact 20 ridge extending spirally about izhe axis of said stem the said ridge being adapted to be slightly distorted to provide a spring-dike pressure fit with a bore of llesser diameter man the free diameter of the stem.

A. A sieczym' wiizcii ccmgcricmg in ccmbmmiaicia,

a parcel comprising a piumiiiy 0i meusiiic cic memes each maimed ic form pact ci 2m cicci'zicai circuit, smdwicilc ni 942 1611 ccmcmcai bctwccn cic mcnis ci' ncmcomiucting mat 2mm, a cyiimiicai hcicihmugh said panel picscmmg @GXIMLCE oi limiiczi arc at the surface uhcx'cci ci each of mctcqliic clement-s, mtambic plug in imic pmvic'icci with apmzimmtciy mic and @E'ifi ififiif iums ci spimimisc wiwcc ircc' ciiamcicc cxcccclc izhct of said mic hearing 1m iimiicfi arc ci said surface in the plane cf each cicmcxii; moi adapted in contact said mctcdiiic cicmcmc singly in succccsiom as the said plug is mugged and means ion" Rimming the mini movement ci mid mug.

@QMQN R. PEYMNGTUN.

UNITED STATES PATENTS Name Date Biricmer Jan. 27, 1897 Victor -m Jan. 11, 1921 Number 

